Keyboard Events are ways we can design software to response to user input through the keyboard. There aren't a lot of instances where we want to actively interfere while the user types, but the few times we do, can provide a great deal of convenience and reduce headache. For example, consider a text field where a user is expected to provide a phone number. By all the old gods and the new ones, I certainly hope you don't expect the user to follow any particular format when attempting this, as you both will likely be disappointed. Instead, use Keyboard Events to "help" them complete the format.

For example, let's say you want to enforce the following template: (XXX) XXX-XXXX. You can use Keyboard Events (1) to detect when the user begins to enter in a phone number (based on which text field currently has "focus") (2) determine if the characters entered are digits (and to reject any that are not) and (3) based on the number of digits they've entered, automatically include the (, ), and - characters as necessary. "if (phoneField.Text.Length == 4)", then its time to automatically append the closing parentheses and padding space characters. This way, users can enter their phone numbers from a num pad (if their keyboard has one) or at the very least, without including the non-digit characters, and you can enforce a specific template. Everybody wins!

There are three Key events: KeyDown, KeyPress, and KeyUp, relating to when you first push down a key, while the key is being pressed, and finally the key being released. The KeyEventArgs class has properties that can tell us more details about the key sequence being used (i.e. are you typing 'a' or 'A'). Three boolean properties called Alt, Control, and Shift, indicating whether these keys are a part of this sequence. The Keys KeyCode identifies which key has been pressed by an enumeration group, with members listed as Keyse.A and Keys.PageDown, for example. Finally, there's a int KeyValue to identify key codes by their ASCII value (which I personally think is silly to use if you can simply code the target key codes by their typable character/phrase.)

There's also a KeyPressEventArgs class that contains a particularly useful property, char KeyChar, which contains the value of the ASCII character produced by the user's key sequence input.